sd-login: rework error handling

Makre sure we always return sensible errors for the various, following
the same rules, and document them in a comment in sd-login.c. Also,
update all relevant man pages accordingly.

7 files changed, 222 insertions, 20 deletions

diff --git a/man/sd_get_seats.xml b/man/sd_get_seats.xml
index 4390d36ebe..f1981f7ea2 100644
--- a/man/sd_get_seats.xml
+++ b/man/sd_get_seats.xml
@@ -115,6 +115,29 @@
     errno-style error code.</para>
   </refsect1>
 
+
+  <refsect1>
+    <title>Errors</title>
+
+    <para>Returned errors may indicate the following problems:</para>
+
+    <variablelist>
+
+      <varlistentry>
+        <term><constant>-EINVAL</constant></term>
+
+        <listitem><para>An input parameter was invalid (out of range,
+        or NULL, where that's not accepted).</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><constant>-ENOMEM</constant></term>
+
+        <listitem><para>Memory allocation failed.</para></listitem>
+      </varlistentry>
+    </variablelist>
+  </refsect1>
+
   <refsect1>
     <title>Notes</title>
 
diff --git a/man/sd_login_monitor_new.xml b/man/sd_login_monitor_new.xml
index a7b47a3207..a8854dd590 100644
--- a/man/sd_login_monitor_new.xml
+++ b/man/sd_login_monitor_new.xml
@@ -161,20 +161,20 @@
     is no timeout to wait for this will fill in <constant>(uint64_t)
     -1</constant> instead. Note that <function>poll()</function> takes
     a relative timeout in milliseconds rather than an absolute timeout
-    in microseconds. To convert the absolute 'us' timeout into
+    in microseconds. To convert the absolute 'µs' timeout into
     relative 'ms', use code like the following:</para>
 
     <programlisting>uint64_t t;
 int msec;
 sd_login_monitor_get_timeout(m, &amp;t);
 if (t == (uint64_t) -1)
-  msec = -1;
+         msec = -1;
 else {
-  struct timespec ts;
-  uint64_t n;
-  clock_getttime(CLOCK_MONOTONIC, &amp;ts);
-  n = (uint64_t) ts.tv_sec * 1000000 + ts.tv_nsec / 1000;
-  msec = t > n ? (int) ((t - n + 999) / 1000) : 0;
+         struct timespec ts;
+         uint64_t n;
+         clock_getttime(CLOCK_MONOTONIC, &amp;ts);
+         n = (uint64_t) ts.tv_sec * 1000000 + ts.tv_nsec / 1000;
+         msec = t > n ? (int) ((t - n + 999) / 1000) : 0;
 }</programlisting>
 
     <para>The code above does not do any error checking for brevity's
@@ -204,6 +204,29 @@ else {
   </refsect1>
 
   <refsect1>
+    <title>Errors</title>
+
+    <para>Returned errors may indicate the following problems:</para>
+
+    <variablelist>
+
+      <varlistentry>
+        <term><constant>-EINVAL</constant></term>
+
+        <listitem><para>An input parameter was invalid (out of range,
+        or NULL, where that's not accepted). The specified category to
+        watch is not known.</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><constant>-ENOMEM</constant></term>
+
+        <listitem><para>Memory allocation failed.</para></listitem>
+      </varlistentry>
+    </variablelist>
+  </refsect1>
+
+  <refsect1>
     <title>Notes</title>
 
     <para>The <function>sd_login_monitor_new()</function>,
diff --git a/man/sd_machine_get_class.xml b/man/sd_machine_get_class.xml
index 5b881ccea1..9ad7f3fc66 100644
--- a/man/sd_machine_get_class.xml
+++ b/man/sd_machine_get_class.xml
@@ -56,7 +56,7 @@
       <funcprototype>
         <funcdef>int <function>sd_machine_get_class</function></funcdef>
         <paramdef>const char* <parameter>machine</parameter></paramdef>
-        <paramdef>char *<parameter>class</parameter></paramdef>
+        <paramdef>char **<parameter>class</parameter></paramdef>
       </funcprototype>
 
       <funcprototype>
@@ -99,6 +99,35 @@
   </refsect1>
 
   <refsect1>
+    <title>Errors</title>
+
+    <para>Returned errors may indicate the following problems:</para>
+
+    <variablelist>
+
+      <varlistentry>
+        <term><constant>-ENXIO</constant></term>
+
+        <listitem><para>The specified machine does not exist or is currently not running.</para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><constant>-EINVAL</constant></term>
+
+        <listitem><para>An input parameter was invalid (out of range,
+        or NULL, where that's not accepted).</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><constant>-ENOMEM</constant></term>
+
+        <listitem><para>Memory allocation failed.</para></listitem>
+      </varlistentry>
+    </variablelist>
+  </refsect1>
+
+  <refsect1>
     <title>Notes</title>
 
     <para>The <function>sd_machine_get_class()</function> and
diff --git a/man/sd_pid_get_session.xml b/man/sd_pid_get_session.xml
index 9c6706caf8..903c143f36 100644
--- a/man/sd_pid_get_session.xml
+++ b/man/sd_pid_get_session.xml
@@ -1,4 +1,4 @@
-<?xml version='1.0'?> <!--*-nxml-*-->
+<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
 
@@ -163,7 +163,7 @@
     processes, user processes that are shared between multiple
     sessions of the same user, or kernel threads). For processes not
     being part of a login session this function will fail with
-    -ENXIO. The returned string needs to be freed with the libc
+    -ENODATA. The returned string needs to be freed with the libc
     <citerefentry
     project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
     call after use.</para>
@@ -175,9 +175,9 @@
     paths. Note that not all processes are part of a system
     unit/service (e.g. user processes, or kernel threads). For
     processes not being part of a systemd system unit this function
-    will fail with -ENXIO (More specifically: this call will not work
-    for kernel threads.) The returned string needs to be freed with
-    the libc <citerefentry
+    will fail with -ENODATA (More specifically: this call will not
+    work for kernel threads.) The returned string needs to be freed
+    with the libc <citerefentry
     project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
     call after use.</para>
 
@@ -194,7 +194,7 @@
     multiple login sessions of the same user, where
     <function>sd_pid_get_session()</function> will fail. For processes
     not being part of a login session and not being a shared process
-    of a user this function will fail with -ENXIO.</para>
+    of a user this function will fail with -ENODATA.</para>
 
     <para><function>sd_pid_get_machine_name()</function> may be used
     to determine the name of the VM or container is a member of. The
@@ -203,7 +203,7 @@
     <citerefentry
     project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
     call after use. For processes not part of a VM or containers this
-    function fails with -ENXIO.</para>
+    function fails with -ENODATA.</para>
 
     <para><function>sd_pid_get_slice()</function> may be used to
     determine the slice unit the process is a member of. See
@@ -251,7 +251,22 @@
     <variablelist>
 
       <varlistentry>
-        <term><constant>-ENXIO</constant></term>
+        <term><constant>-ESRCH</constant></term>
+
+        <listitem><para>The specified PID does not refer to a running
+        process.</para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><constant>-BADF</constant></term>
+
+        <listitem><para>The specified socket file descriptor was
+        invalid.</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><constant>-ENODATA</constant></term>
 
         <listitem><para>Given field is not specified for the described
         process or peer.</para>
@@ -259,11 +274,10 @@
       </varlistentry>
 
       <varlistentry>
-        <term><constant>-ESRCH</constant></term>
+        <term><constant>-EINVAL</constant></term>
 
-        <listitem><para>The specified PID does not refer to a running
-        process.</para>
-        </listitem>
+        <listitem><para>An input parameter was invalid (out of range,
+        or NULL, where that's not accepted).</para></listitem>
       </varlistentry>
 
       <varlistentry>
diff --git a/man/sd_seat_get_active.xml b/man/sd_seat_get_active.xml
index 3c57ec9ea4..4d3e0822e0 100644
--- a/man/sd_seat_get_active.xml
+++ b/man/sd_seat_get_active.xml
@@ -149,6 +149,43 @@
   </refsect1>
 
   <refsect1>
+    <title>Errors</title>
+
+    <para>Returned errors may indicate the following problems:</para>
+
+    <variablelist>
+
+      <varlistentry>
+        <term><constant>-ENODATA</constant></term>
+
+        <listitem><para>Given field is not specified for the described
+        seat.</para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><constant>-ENXIO</constant></term>
+
+        <listitem><para>The specified seat is unknown.</para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><constant>-EINVAL</constant></term>
+
+        <listitem><para>An input parameter was invalid (out of range,
+        or NULL, where that's not accepted).</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><constant>-ENOMEM</constant></term>
+
+        <listitem><para>Memory allocation failed.</para></listitem>
+      </varlistentry>
+    </variablelist>
+  </refsect1>
+
+  <refsect1>
     <title>Notes</title>
 
     <para>The <function>sd_seat_get_active()</function>,
diff --git a/man/sd_session_is_active.xml b/man/sd_session_is_active.xml
index 4ca3a6c150..7de9523789 100644
--- a/man/sd_session_is_active.xml
+++ b/man/sd_session_is_active.xml
@@ -290,6 +290,43 @@
   </refsect1>
 
   <refsect1>
+    <title>Errors</title>
+
+    <para>Returned errors may indicate the following problems:</para>
+
+    <variablelist>
+
+      <varlistentry>
+        <term><constant>-ENXIO</constant></term>
+
+        <listitem><para>The specified session does not exist.</para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><constant>-ENODATA</constant></term>
+
+        <listitem><para>Given field is not specified for the described
+        session.</para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><constant>-EINVAL</constant></term>
+
+        <listitem><para>An input parameter was invalid (out of range,
+        or NULL, where that's not accepted).</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><constant>-ENOMEM</constant></term>
+
+        <listitem><para>Memory allocation failed.</para></listitem>
+      </varlistentry>
+    </variablelist>
+  </refsect1>
+
+  <refsect1>
     <title>Notes</title>
 
     <para>The <function>sd_session_is_active()</function>,
diff --git a/man/sd_uid_get_state.xml b/man/sd_uid_get_state.xml
index b158f3528c..13ddf08c65 100644
--- a/man/sd_uid_get_state.xml
+++ b/man/sd_uid_get_state.xml
@@ -170,6 +170,45 @@
   </refsect1>
 
   <refsect1>
+    <title>Errors</title>
+
+    <para>Returned errors may indicate the following problems:</para>
+
+    <variablelist>
+
+      <varlistentry>
+        <term><constant>-ENODATA</constant></term>
+
+        <listitem><para>Given field is not specified for the described
+        user.</para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><constant>-ENXIO</constant></term>
+
+        <listitem><para>The specified seat is unknown.</para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><constant>-EINVAL</constant></term>
+
+        <listitem><para>An input parameter was invalid (out of range,
+        or NULL, where that's not accepted). This is also returned if
+        the passed user ID is 0xFFFF or 0xFFFFFFFF, which are
+        undefined on Linux.</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><constant>-ENOMEM</constant></term>
+
+        <listitem><para>Memory allocation failed.</para></listitem>
+      </varlistentry>
+    </variablelist>
+  </refsect1>
+
+  <refsect1>
     <title>Notes</title>
 
     <para>Functions described here are available as a shared library,